DALLAS -- On a stormy day in January, Charlotte Allison and Cheryl Sherman boarded planes heading in opposite directions, two sisters on a common mission.

Charlotte was on her way from Los Angeles to Dallas to stay with their 77-year-old mother, who was dying of cancer. Cheryl was traveling home to Northern California after a grueling week by their mother's side. For three months, the sisters had been swapping off at least twice a month in an increasingly familiar kind of family commute: the cross-country death vigil.

Valliere Wilson's three children grew up in Dallas but all eventually wound up on the West Coast, going back to Texas to visit their mother once or twice a year. In 2003, they learned that the cancer Ms. Wilson had battled for more than a decade had spread. Doctors suggested she had little time left. Her children rallied around to see her through.

Their devotion bore a high price. Ms. Wilson's son, Ed Sherman, 58, moved back to Dallas, straining his marriage to the breaking point. Cheryl, 54, and Charlotte, 50, exhausted themselves traveling between California and Texas. Juggling vacation days, telecommuting and family leave, the sisters worried about losing their jobs and struggled through their grief to keep up appearances at work.

When a parent is dying, the rest of life waits. Now, it often waits longer. As medical science gets better at pulling terminally ill patients from the brink of death, a loved one's final weeks can stretch into months or years. With families often spread across the country or globe, far-flung relatives face heart-rending choices as they wait for the end.

Hospice workers say counseling out-of-town relatives when to rush home becomes an excruciating guessing game. There are certain clues -- mottled skin, a rattle in the chest -- that can send a child racing to the airport. But patients sometimes rally just as the family gathers to say goodbye.

"You think death is occurring, you come, and you make that last, completing visit. Then you go home and a month later, you find that they're still there. You have to go back," said Dave Leisure, a social worker with the Community Hospice of Texas in Fort Worth.

Jane Swanson worried she wouldn't be able to be there when her mother died after a long illness in 2005. "My mother brought me into this world, and it was important to me to help her leave the world," she said. "I didn't want to do that from afar."

Ms. Swanson, then an administrative worker at a Houston software company, took eight trips to her parents' home in Columbus, Ohio, staying weeks at a time. She used up all her vacation and sick time, and then took a family leave. She ran up more than $5,000 in airfare and estimates she lost $15,000 in salary. "Thank God for credit cards," she said.

After Ms. Swanson's mother died, her 88-year-old father declined quickly. She took more time off work, raising eyebrows in her company's human-resources department. "I've lost my mother and I'm losing my father," she told two human-resources managers in a meeting. "I really don't care what you think about that."

Not all adult children go to extremes to be with a dying parent. They make a final goodbye visit, and then wait for the funeral. Pressure from bosses or spouses prevent some people from being there, says Ken Doka, a professor of gerontology at the College of New Rochelle in New York. And those decisions often echo long beyond the funeral. "After, they might say, 'I wish I had gone sooner. I wish I'd spent more time,'&nbsp;" he says.

In interviews over the course of seven months, Valliere Wilson's children described their efforts to be at their mother's side.

Ms. Wilson grew up in Dallas, raised in the Depression era by her grandmother. When she was 18 years old, she married a career Army officer and had her two eldest children, Ed and Cheryl. She divorced, married again, and Charlotte was born. Her second marriage ended when Charlotte was five. For the next decade she was a single mother, working as many as three waitress and drugstore-clerk jobs at one time while Cheryl and Charlotte shouldered the household chores.

Tough times cemented a bond between Ms. Wilson and her children. "She never wanted us to feel like we were suffering," says Charlotte. When Charlotte was 15, her mother married for a third time.

Ed left home at 17 and hitchhiked to Canada with "just a Bible and a carton of cigarettes," he says. Cheryl moved away after college. Both Ed and Cheryl wound up in Northern California, visiting their mother in Dallas every couple of years. Charlotte stayed in Dallas, where she raised her own two children before divorcing.

After Ms. Wilson's third husband died in 1991, she remained in their brick home on a tree-lined north Dallas street. Whenever family arrived for a visit, she would throw open the front door and say, "Get yourself in here!" In 1992, she was diagnosed with colon cancer, and battled its progression with surgery and five rounds of chemotherapy.

Cheryl called every day after work to check in, and flew to Dallas for major doctor visits and surgery. But as the one still living in Dallas, Charlotte provided most of the care for her mother during the long, roller-coaster illness. "I was always the child who stayed home," she said.

In late 2003, Charlotte, then a marketing specialist for TicketMaster, accepted a job with a new sports arena in Memphis, Tenn. Two days before she moved, her mother got the results from a CAT scan: The cancer had spread again, this time to her lungs. Ms. Wilson urged her daughter to take the Memphis job anyway. Still, in an interview last December, Ms. Wilson said she kept imagining herself spending her last hours surrounded by strangers. "Oh, I wish my kids lived here," she remembered thinking when her daughter moved away.

Charlotte was racked with guilt. She reassured her mother that the 450 miles between Memphis and Dallas was "driving distance," and that she'd come home often.

With Charlotte gone, Ed's wife, Patty, suggested moving to Texas. There Ed, who had recently completed a college degree, could launch a career as a math teacher. In the summer of 2004, Ed and his wife left their rural Northern California home of nearly 20 years and moved to Dallas. "It was the right thing to do," Ed said.

In 2006, Ms. Wilson's condition worsened. She battled repeated lung infections with course after course of antibiotics and steroids. The sicker their mother got, the more stress Charlotte and Cheryl felt trying to deal with it long-distance.

By then, Charlotte had moved again, to Los Angeles. She persuaded her mother to get a cellphone, and on doctor days, Charlotte would wait anxiously at her desk, dreading more bad news and thinking, "Oh God, my mom's going to call any minute."

Further north in San Ramon, Calif., Cheryl was trying to keep her composure as a manager at a major telecommunications firm. She'd learned to take calls from her mother in a conference room to avoid the risk of crying in her cubicle. Most of her co-workers knew about her mother's illness, but some were reluctant to ask about it. "I'd just start crying and wave my hands and have to go to the bathroom," Cheryl said.

Ed faced his own crisis. He and his wife went back for a visit to California in the summer of 2006. Ed returned to Texas alone. Patty said she hated to abandon Ms. Wilson, but after living all her adult life in the country, she felt out of place in the steel and concrete of the city. "When it came time to go back for the third winter I literally, physically, at a cellular level, could not go," she said.

With his marriage of 30 years on the rocks, Ed sank into a funk. He went days without talking to his mom. He worried that he should be paying her more attention. But, he said, "I'm only a half hour away, which is better than being 2,000 miles away. That's what I tell myself."

In September 2006, a new CAT scan revealed Ms. Wilson's lungs were filling with fast-growing tumors. For years, she had nagged her oncologist to tell her how long she had left, and he would always tell her he didn't know. This time, he told her: "Three to six months."

Charlotte urged her mother to keep fighting. During Cheryl's trips to Dallas, she and her mother would sometimes spend the whole day in their pajamas, reminiscing and gossiping. Ed didn't always get along with his sisters, but he was there to patch his mom's roof or wrap the pipes in cold weather. On weekends, he'd help with grocery shopping.

At her doctor's suggestion, Ms. Wilson registered with a local hospice, VistaCare, to provide home care and assistance with medications. Charlotte and Cheryl arranged for one of the daughters to be there at least every other week. Ed was to fill in as necessary. As their mother got worse, the two sisters would come more often, and both planned to be there round-the-clock at the end.

Ms. Wilson was elated. "Why would I even think that they could come, that their bosses would let them?" she said. "I was the happiest person in the world when they told me what they were going to do."

Worried about the expense, Ms. Wilson insisted on paying for her daughters' air travel. Cheryl and Charlotte worked out a schedule so that they could buy cheaper advance tickets. Cheryl took out a new credit card to handle the charges.

In October, Ms. Wilson's doctor inserted a stent to open her tumor-clogged airways and help her breathe better. Ms. Wilson improved enough that she didn't need anyone with her. She could still cook for herself, and she even made it to her weekly bridge games, packing along her oxygen tank.

Still, the sisters kept up their travel rotation from California. Charlotte installed a high-speed computer line in her mother's home so she could telecommute while visiting. Cheryl struck an agreement with her supervisor to work out of the company's Dallas office while she was in town. They wanted to spend time with their mom while she was still able to laugh and play "down-and-dirty Uno," the family version of a card game.

During Cheryl's visit the first week in December, Ms. Wilson coughed up the stent that had helped her breathe. Cheryl struggled to reassure her mother while holding back her own tears.

Ed hadn't called his mother that week. His detachment frustrated his sisters, but his mother worried that Ed had too much on his mind. Ms. Wilson waited several days before phoning him to tell him about the stent. "I know how you react when the phone rings," she told him.

"I do react poorly," Ed admitted. "Sometimes the answering machine will blink for days, but I won't listen to it because I'm afraid it's bad news."

Charlotte returned to Dallas to spend her last Christmas with her mother. For the first time in her life, Ms. Wilson was too weak to help cook Christmas dinner. She had to sit on the couch and watch while Charlotte made a mess of the chocolate pie. "That nearly killed me," Ms. Wilson said.

Ms. Wilson turned the corner into a new year. Her children began thinking that maybe the doctors were wrong. Maybe their mother would have more time.

On Feb. 20, Cheryl was with her mother in Dallas, missing a staff meeting in Chicago. She grew worried about rumored layoffs at work. For the first time in her 26 years at the company, she'd gotten a poor annual review, based on low productivity. She'd asked for more work, but her supervisor had noted that it was probably better that she not be stretched while she was dealing with her mom. Cheryl acknowledged, "Actually, I couldn't handle any more."

Meanwhile, Charlotte had just been told that her company's Los Angeles office was closing at the end of the year and she would be out of a job. Cracks had begun surfacing in her longtime relationship with her boyfriend. "Everything was kind of falling to pieces," she said.

By mid-March, there was a marked change in their mother. She was more anxious and couldn't sustain a conversation without getting winded. For the first time, she began to take morphine during the day. "She's declining pretty rapidly," warned Vicki Rhodes, the hospice nurse.

Cheryl told her domestic partner, Rae Morgan, that she thought she should begin spending more time in Dallas. Ms. Morgan had been supportive, but now she protested, worried about the strain Cheryl already was under, and how Cheryl's boss might react. Cheryl didn't want to hear it. "I could have strangled her because that just added more stress," Cheryl said.

Charlotte took drastic action. At the end of March, she told her boss she was moving back to Dallas, and asked permission to telecommute until her job ended later that year. He agreed, and she scheduled the movers.

On March 28, Charlotte arrived in Dallas for her last visit before her move. Her mother had begun losing weight rapidly and was suffering more bouts of confusion. "We're looking at less than a month," Ms. Rhodes told the children.

Over the next few days, Charlotte and her mother clashed. Her mother was uncharacteristically critical of Charlotte's efforts to help her. Charlotte called Cheryl in California for support. On April 5, Cheryl wrote in an email, "Charlotte and I are physically and emotionally exhausted."

The next day, Ms. Wilson woke up confused and obstinate, refusing to take her medicine. When the nurse arrived, she found Ms. Wilson looking pale and weak. She pulled Charlotte aside. "You can't leave your mother alone," she told her.

That night, Ms. Wilson had more trouble breathing after she went to bed. She woke in a panic around midnight and asked Charlotte for morphine. An hour later, she called out again, and Charlotte gave her another half-dose of morphine. Forty-five minutes later, she called for Charlotte once more. Charlotte was worried about giving too much painkiller, so she gave her an anxiety medication. Her mother was quiet the rest of the night.

Shortly after 6 a.m., Charlotte went in to check on her mom. Ms. Wilson lay on her side, her head on her pillow. "She's still asleep," Charlotte thought, describing the scene later. But when she dropped something on the floor, her mother didn't stir. She put her hand on her mother's arm. Her body was cold. "No!" Charlotte wailed. "Please don't do this." She lay her head down next to her mother and held her.

Cheryl knew what it meant when her phone rang at 4:30 a.m. in California. "I was preparing myself," she said. But hearing the news by phone was still hard. "I wasn't there when she died, and I wasn't there to help Charlotte to deal with it," she said. Ed drove straight over when he got Charlotte's call, and together the brother and sister sat with their mom, holding her hand and saying goodbye. "You know," Ed told Charlotte, "Cheryl is going to have different memories because she wasn't here for this."

Charlotte returned to work in Los Angeles a few days after the funeral; her plans to move to Dallas are on hold. Ed submitted his resignation to the school where he taught, and will return to California in June to try to repair his marriage. He says if he had to do it over, he'd still move to be closer to his mother. "She loved that I was here for her," he said.

Cheryl took a week off work to grieve, and then returned to her San Ramon office. She was greeted by sympathetic co-workers, which made her cry again.

She has no regrets. She hadn't been there with her mom when she died, but she sees the time she spent when she was alive as more important. "I always told Mom that I would be there for her when she needs me, and I was," she said.

Bone weary, Cheryl thought about canceling a visit to see her father on May 10, but he seemed distressed by the idea. He's 87 years old, and he lives in Las Vegas, so she decided to go after all. "And I'm going to tell him, 'If you want me, I'll be there for you, too."'

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